Mixing to different RAM speeds -- it will want to be clocked at the slower speed RAM. As far as the 1866 speed memory, the board claims it supports that speed with an OC / XMP profile, however sometimes that doesn't work correctly depending on the board BIOS rev & RAM compatibility.

I would reset everything to default in the BIOS, then try to get it working with the DDR3-1600 speed memory. If that works, take it out and insert just the DDR3-1866 speed memory, then if it boots, go into the BIOS and test out which XMP profiles work. It might take a few tries and clearing the CMOS if it freezes..

Agree ! According to the manual any ram faster than 1600 is OC. The QVL list for that board has a very short "supported" list for 1866 ram.
One thing that happens is the SPD profiles may not match well (happens when mixing speeds, much worse when mixing speeds and manufactures).
Example: the 1600 SPD may have 1600 and 1333 speeds listed, the 1833 may only have 1833 listed or 1833 and 1067.
There is no way for the board to Auto set proper mem speed when things are that way so assumes are trying to OC the 1600 to the 1866...
I have had that issue and had to force manually the mem speed and timing.
Always make sure your slowest speed ram is in the first slot/or first channel, that can help.
added: I suggest you do as wiretap says and then once up in windows run CPUZ and check the SPD timings and voltages of the 1600 (write them down). Then remove 1600 and try the 1833,
if you get it back into windows run CPUZ again and check the SPD timings again.

Once again, what are these memory modules made by? Does matter.

You can find OEM made memory modules in 1866MHz means good SPD data that will work on yours guaranteed.

Also you can use ECC 1866MHz modules and motherboard will ignore the ECC part. Easier to get this way. This will either run at 1600 or 1866 if CPU supports these. Of coruse you can "overclock" CPU to use 1866MHz via bios settings.

Another thing, notice I didn't provide examples that is sold by chinese sellers. These chinese sellers are selling fakes with same serial number on all of the memory modules. Genuine OEM quality modules have unique serial programmed in each to vertify they are real product.
Another reason I no longer recommend the memory modules from third party except Kingston due to SPD programming is not good. Example. I had pair of Corsair DDR3 that is advertised as DDR3-1600, no where it mentioned that was overclocking, XMP mode or runs at 1333. On 2 boards that supports DDR3 1600 (CPU and motherboard are rated for this), this memory modules ran at DDR3 1333. On one of this, I had to set as XMP to run 1600. That's incorrect since the modules says it is for 1600. I ended up cloning a SPD data from a good OEM DDR3 1600 on both to run at 1600 properly. This is reason to avoid that and prevents adding complexity of the problems like you had.

Examples:
https://www.ebay.ca/itm/126122489963?hash=ite … ABk9SR6TkpP6WYw

https://www.ebay.ca/itm/126122489963?hash=ite … ABk9SR6TkpP6WYw

Cheers,

Thanks for the replies!
With the 1600 memory the board runs fine, but it won’t run with the 1866 sticks.
I can‘t get it to work but oh well…